When a transmitting terminal needs to send data packets of a data flow, the transmitting terminal selects an appropriate transport protocol to send the data packets according to its requirements. There are many transport protocols, and one of them is the Transmission Control Protocol (TCP). According to TCP protocol, when a receiving terminal receives a data packet of a data flow, the receiving terminal reply by sending a reception acknowledgement message to the transmitting terminal informing that the data packet has been received by the receiving terminal. Then the transmitting terminal continues to send other data packets of the data flow. Also, the transmitting terminal uses the information of the reception acknowledgement message and the received time of the reception acknowledgement message to determine the transmission rate.
When a plurality of network connections simultaneously send the data packets of the data flow, the transmission rate can be improved. However, the data packets may not be received by the receiving terminal in correct order, it is possible for the receiving terminal to consider that it failed to receive some of the data packets. As a result, the receiving terminal may not promptly send the reception acknowledgement message to the transmitting terminal. Further, the reception acknowledgement message may not be received by the transmitting terminal sequentially, and hence the transmitting terminal may not calculate the transmission rate accurately. These can make the transmitting terminal unable to simultaneously send the data packets of a data flow at the maximum speed of the plurality of network connections.